Economical and flexible provision of electric power and cooling is an important aspect of modern large-scale computer data centers. Such data centers may house thousands, hundreds of thousands, or even millions of computer servers mounted in numerous rows of computer racks, and those computers may be used for a variety of computing functions. The computers use electric power to perform the computations and other related activities, and the power usage is relatively dense (megawatts of power in a single facility). As a result, the computer servers and related components generate a large amount of heat. For example, a pair of microprocessors mounted on a single motherboard can draw 200-400 watts or more of power. Multiply that figure by several thousand (or tens of thousands) to account for the many computers in a large data center, and one can readily appreciate the amount of heat that can be generated.
While the cost of generating the heat (in terms of electrical usage) can be high for a data center, the cost of removing all of the heat can also be high. That cost typically involves the use of even more energy, in the form of electricity and natural gas, to operate chillers, condensers, pumps, fans, cooling towers, and other related components. Heat removal can also be important because, although microprocessors may not be as sensitive to heat as are people, increases in heat generally can cause great increases in microprocessor errors and failures. In sum, such a system may require electricity to run the chips, and more electricity to cool the chips.